1. Field of the Invention
The present invention relates to a curtain airbag that inflates and deploys along a side surface portion in a vehicle interior in order to protect an occupant when the vehicle is subjected to a side impact crash or a rollover.
2. Related Technology
In recent years, vehicles are required to meet higher safety standards. This trend is common throughout the world and most vehicles come equipped with airbags as a safety apparatus throughout the world. Further improvement of safety is an important development theme held out by operators involved in development of vehicles. Accordingly, new airbags are being developed on a daily basis.
Evaluation standards for the safety of vehicles vary among the countries, and the operators develop airbags so that manufactured articles of the operators meet the evaluation standards of many countries. For example, in the U.S., which has the largest number of automobiles owned in the world, National Highway Traffic Safety Administration (NHTSA) has established Federal Motor Vehicle Safety Standards (FMVSS). The Notice of Proposed Rule Making (NPRM: Docket Number; NHTSA-2009-0183) for FMVSS specified by NHTSA proposes the requirement that “upon a side impact crash or a rollover, an ejection mitigation system reduces the likelihood that an occupant is thrown out of the vehicle though a side window”. The requirement can be achieved by providing the vehicle with a curtain air bag serving as an exterior ejection mitigation countermeasure apparatus providing an ejection mitigation system. The Notice of Proposed Rule Making (NPRM: Docket Number; NHTSA-2009-0183) referred to herein bases formally established FMVSS226.
The curtain airbag is an airbag installed in the upper part of doors and which inflates and deploys along the side windows of the vehicle when an impact occurs. A cushion portion of the curtain airbag which corresponds to an inflated area is partitioned into a plurality of small rooms (chambers) for the purpose of, for example, implementing smoother flow.
Japanese Patent Application Laid-open No. 2008-6895 discloses a curtain airbag with an end chamber installed at an end of the airbag in a front-rear direction of the vehicle and which inflates and deploys toward the interior of the vehicle more significantly than the other chambers. In the curtain airbag, a tension cloth is passed from the inflated area on a central side of the airbag in the front-rear direction of the vehicle through an exterior side of the end chamber to a front pillar. The tension cloth is tensioned when the curtain airbag inflates and deploys, to move the end chamber so that the end chamber is pushed toward the interior of the vehicle.
In evaluation tests on exterior ejection prevention performance specified in NPRM (NHTSA-2009-0183) in the U.S., an impactor is defined in V. “Proposed Ejection Mitigation Requirements and Test Procedures” of NPRM (NHTSA-2009-0183). Impact targets for the impactor are defined as target locations specified in V. “Proposed Ejection Mitigation Requirements and Test Procedures”, d. “Locations Where the Device Would Impact the Ejection Mitigation Countermeasure to Assess Efficacy”, and 4. “Method for Determining Impactor Target Locations” of NPRM (NHTSA-2009-0183), which is herein incorporated by reference. These break points are illustrated by target break points described in NPRM, for example, points shown at A1 to A4, B1 to B4, and the like. In the present application, the break point shown as A1 is referred to as the “A1 break point”.
There is presently a demand for further improvement of the occupant exterior ejection prevention performance of the curtain airbag. For improvement of the exterior ejection prevention performance, an efficient method is to contact and restrain the occupant early. This is because the early restraint correspondingly reduces the amount by which the occupant is moved toward the exterior of the vehicle.
In this regard, the curtain airbag described in Japanese Patent Application Laid-Open No. 2008-6895 allows the wide tension cloth to push the end chamber toward the interior of the vehicle and thus inflates and deploys at a position closer to the occupant than conventional curtain airbags. Consequently, this curtain airbag can come into contact with the occupant early.
However, the technique described in Japanese Patent Application Laid-Open No. 2008-6895 improves the exterior ejection prevention performance simply by passing the wide tension cloth, which contacts the end chamber over a wide area, through the exterior side of the end chamber. In addition, when the tension cloth is used, the curtain airbag includes a large cloth portion and is thus bulky and difficult to house when the curtain airbag is folded. Furthermore, in this case, the curtain airbag is disadvantageously applicable only to vehicles with a large front pillar.
On the other hand, when a narrow strap is used instead of the wide tension cloth in order to allow the curtain airbag to be more appropriately housed, the area over which the end chamber is supported when the occupant is thrown out of the vehicle is relatively smaller than when the tension cloth is used. This disadvantageously makes improvement of the exterior ejection prevention performance difficult.
The inventors have found that, when a position where the strap narrower than the tension cloth is attached to the front pillar is taken into account, even the use of the strap avoids sacrificing the exterior ejection prevention performance and rather allows the exterior ejection prevention performance to be improved, while ensuring that the curtain airbag can be appropriately housed on the front pillar.
With these problems in view, it is an object of the present invention to provide a curtain airbag that allows the exterior ejection prevention performance to be improved while being appropriately housed on the front pillar.